The present invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to positively or negatively charged toner compositions, or toner particles containing a mixture of coated silica and coated metal oxides, such as titanium dioxide, surface additives, and yet more specifically, the present invention is directed to toners with surface additives comprised of two coated silicas, and a metal oxide, and wherein one of the silicas is usually a negatively charging silica, and the second silica is a positive charging silica (relative to the carrier), such as H2050EP. With the toners of the present invention, especially wherein the ratio amount of the coated silicas and the coated metal oxides, such as titanium dioxide, is preselected, there is enabled a number of advantages, such as the minimization or elimination of undesirable image background problems, avoiding slow admix charging, and toner charge thru problems; excellent stable triboelectric charging characteristics, reduced sensitivity to relative humidity, especially relative humidities of from about 20 to about 80 weight percent, superior toner flow acceptable triboelectric charging values, such as from about -15 to about -80 microcoulombs per gram as determined, for example, by the known Faraday Cage method, and wherein the toners enable the generation of developed images with superior resolution, and excellent color intensity. The aforementioned toner compositions can contain colorants, such as dyes or pigments comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, orange, violet or brown components, or mixtures thereof, thereby providing for the development and generation of black and/or colored images, and in embodiments the toner can be selected for two component development and single component development wherein a carrier or carrier particles are avoided, and hybrid development systems which contain aspects of both two component and single component development.
Preferred as surface additives are an amino functionalized organopolysiloxane treated silicon dioxide, available as H2050EP from Wacker Chemie, and a decyl silane treated, or coated titanium dioxide available as SMT5103 from Tayca Corporation. More specifically, an example of the first silica is a relatively negative charging silica, NA50HS obtained from DeGussa/Nippon Aerosil Corporation, preferably approximately 30 nanometers of primary particle size and about 350 nanometers of aggregate size, or a fumed silica coated with a mixture of hexamethyldisilazane and aminopropyltriethoxysilane. Another example of the first silica is a relatively negative charging silica, DTMS obtained from Cabot Corporation, comprised of a fumed silica, for example silicon dioxide core L90 of approximately 30 nanometers of primary particle size and about 300 nanometers of aggregate size, and coated with decylsilane. An example of a metal oxide is SMT5103 crystalline titanium dioxide core MT500B, obtained from Tayca Corporation, with a primary particle size of from about 25 to about 55 nanometers and a specific surface of about 30 to about 50 m.sup.2 /g, surface treated or coated with decyl silane. As an example of the second silica, a relatively positive charging silica, H2050EP silica (nonparticulate) with polydimethylsiloxane units or segments, and amino/ammonium functions chemically bonded onto the surface of highly hydrophobic fumed silica, and which coated silica possesses a BET surface area of about 110 to about .+-.20 m.sup.2 /g (obtained from Wacker Chemie). An example of a film-forming additive is a metal salt of a fatty acid, such as zinc stearate L obtained from Ferro Corporation.
The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, including color, digital processes, and multisystems apparatus and machines.